Artificial insemination (AI) has been a standard breeding practice in purebred cattle herds for many years. An AI program is needed to remain competitive for the sale of breeding stock, and to improve traits of economic importance in these herds. There are also viable reasons to use AI in a commercial herd. These include:
- The use of genetics not usually available on a local basis.
- The production of replacement heifers with superior genetics.
- Coupled with estrus synchronization, consolidation of the calving season.
- The need for fewer bulls in the breeding season.
- Higher growth performance and calf value.
- The production of calves for specialty markets such as club calves.
Bull studs have a wide variety of bulls available for AI use. Most breeding and herd improvement objectives can be matched with bulls that are available. This can include traits ranging from weaning weight, milk production, carcass traits, docility and others. These bulls can also provide outcross or crossbred genetics that may not be available locally.
Photo courtesy of Gareth Weeks/sxc.hu.
A major reason to use AI in the commercial herd is the production of replacement heifers. Generally, a within-herd selection program for replacements will be relegated to the progeny of just a few cows in order to make any maternal improvement in the herd. Heifers selected from across the herd will retain little more than average performance. With AI use, sires can be selected specifically for maternal traits such as milk production, calving ease, birth weight, docility and others to provide maternal improvement. The use of expected progeny differences (EPDs) and other selection tools also provides the advantage of simultaneously improving growth, carcass traits and other factors with careful sire selection.
Crossbreeding programs can utilize AI to capture additional heterosis or in the production of replacement females in a terminal sire program. For example, two breeding herds would normally be needed for a crossbreeding program with a two-breed crossbred cow: one herd to produce these replacements, and a second herd bred to terminal sires. The use of an AI program could eliminate the herd used to produce replacements. Reciprocally, the use of AI for a terminal sire would replace this breeding herd, while replacements could be generated by live matings. Traits of economic and herd importance could then be more effectively targeted.
Numerous estrus synchronization (ES) protocols are now available. These programs have been refined and provide the potential for being highly successful in reducing the labor of estrus detection and consolidation of AI activity. You can review the protocols in general use presented by the Iowa Beef Center website (www.iowabeefcenter.org/estrus_synch.html).
Advantages for the commercial herd include a more concentrated calving season; reduced observation at calving time; and a more uniformly aged calf crop to assist in weaning and marketing management.
The use of AI and ES is not without additional cost, and Table 1 (page 28) provides an outline of possible costs. The costs and returns in the table are based on actual costs incurred in the Pennsylvania Heifer Development Program, and the returns are an average from several years of AI and ES programs in Penn State herds. Note that there is variability in the rate of estrus and the pregnancy rate across farms.
Nutrition, health, general management, semen management and technician proficiency will significantly affect the results of an AI program. In general, the results in Table 1 show it will cost about $100 in many cases to produce an AI calf. Simply from a production standpoint, about 70 to 80 pounds of additional weaning weight for steer calves, or as little as 10 extra pounds of weaning weight per year for the life of a replacement heifer from the AI sire, will cover the cost. Any additional advantages from crossbreeding heterosis, calving ease or milk production are also captured.
Timed AI (TAI) is a procedure where synchronization is coupled with breeding with no observation of the cattle for signs of estrus. Cattle are simply run through the chute at the appointed time and bred. The refinement of ES protocols has made this process available. Our experience with the Pennsylvania Heifer Development Program over two years was that we could consistently achieve 66 percent pregnancy rates with TAI. Other reports have shown there is the normal variability across farms (40 to 80 percent pregnancy rates). Provided the ES protocol has been administered correctly, an advantage of TAI is getting some cows and heifers bred that show no signs of estrus from observation.
Any cows or heifers that are bred by AI do not require a bull. Bulls are generally one of the cheapest and best investments in a commercial cow herd, but an effective AI program can easily cut bull needs in half. For the 30-cow herd, this means even a yearling bull may be all that is needed to clean up breeding.
Sexed semen is now widely available for AI programs. This technology provides a significant advantage for the production of replacement heifers or for the production of club calves. However, sexed semen is more costly, so the need for expert and effective administration of AI and ES programs is magnified. In addition, J.B. Hall (2011) reported that several studies using sexed semen in dairy heifers indicated pregnancy rates that were 10 to 20 percent lower compared to conventional semen (Seidel et al, 1999; Seidel et al, 2000; DeJarnette et al, 2009). Similar data for sexed semen in beef cows and heifers is more limited.
In general, Hall indicated the major AI studs report a 10 to 15 percent reduction in pregnancy rates with sexed semen compared to conventional semen. The high cost of sorting the semen by sex, the loss of 50 percent of an ejaculate when sorting, and a significantly lower number of viable sperm in a straw of semen result in higher cost and lower returns.
Effective health and nutritional management will be the keys to any breeding program, and these features will be even more important in an AI and ES program. However, using AI offers several advantages to the commercial herd.
Dr. John Comerford is an associate professor and extension beef specialist at Pennsylvania State University.